The 57-year-old businessman was a political newcomer in 2014 when he ran a surprisingly strong but ultimately unsuccessful race against incumbent Democratic Gov. Peter Shumlin.

Milne, president of a family-owned travel agency, said in a statement Thursday he would file nominating papers before the deadline for doing so, which was the close of business Thursday at the secretary of state’s office. An official in that office’s elections division later confirmed receipt of Milne’s petitions.

Milne said Leahy, 76, “has never had a real job,” adding that the 42-year Senate veteran is “the definition of a career politician, and I believe career politicians are why our country is in the sad condition it is in.”

A Milne campaign aide did not respond to a follow-up question about whether Milne thinks the U.S. senator position he’d be seeking is not a real job.

Leahy served as Chittenden County state’s attorney before his 1974 election to the Senate.

Milne’s statement did not identify any policy differences with the strongly liberal Leahy.

Milne left himself an out. While the nominating petitions make him an official candidate who will appear on the Republican ballot in the Aug. 9 primary in Vermont, he said in his statement that he “will continue to talk with Vermonters as he explores a potential candidacy,” and plans to make a “formal announcement of his intentions” in July.

Leahy’s campaign manager, Carolyn Dwyer, said Milne “set a new standard in Vermont by running a 100 percent negative campaign before even filing to become a candidate. That may be the Trump way but it’s not the Vermont way,” she added, in a reference to Republican presidential candidate Donald Trump.

Asked whether the Leahy campaign would to try to tie Milne to the Republican standard-bearer, Dwyer said, “Our intention is to focus on an issue oriented campaign, as we have in past campaigns and as we believe Vermonters expect from their candidates. Trump’s name only came up because Mr. Milne is so obviously employing Trump style tactics: ready, fire, aim.”

Leahy, who served as the Senate Judiciary Committee chairman when Democrats were in power, has been a leading supporter of the liberal position on a wide range of issues. He has been outspoken in support of civil rights, women’s rights and gay rights. He played a key Senate role in normalization of relations with Cuba. He’s been critical of the USA Patriot Act and government surveillance directed at electronic communications.

When Milne ran against Shumlin in 2014, Shumlin won with 46.5 percent of the vote to Milne’s 45.2 percent.